1. Field of the Invention
The present invention relates to a semiconductor laser device and a method for making the same and, more particularly, it relates to a semiconductor laser device capable of forming a laser resonator plane in the wafer form and a method for making the same.
2. Description of the Prior Art
Conventionally, a laser resonator plane of a semiconductor laser device has been formed by cleaving an epitaxial wafer into laser bars and such method for cleaving is disclosed in "Be-implanted GaAs/GaAlAs Double Heterostructure Stripe Geometry Lasers Grown by Metalorganic Chemical Vapor Deposition" by H. Shtrikman and D. Fekete, J. Appl. Phys. 56, pp 1298-1300, September 1984.
FIGS. 1A and 1B are cross sectional views showing manufacturing process of a conventional semiconductor laser device mainly formed of a material of AlGaAs system for oscillating short wavelength laser.
To start with, a method for making a conventional semiconductor laser device will be described with reference to FIGS. 1A and 1B.
Referring to FIG. 1A, a buffer layer 13 of p type GaAs is grown on a substrate 7 of p type GaAs. Then, an epitaxial layer group 23 in which laser oscillation is possible is grown on the buffer layer 13, thereby obtaining an epitaxial wafer including the substrate 7, buffer layer 13 and the epitaxial layer group 23. This epitaxial layer group 23 comprises a contact layer 2 of n type GaAs, an upper clad layer 3 of n type AlGaAs, an active layer 4 of p type AlGaAs and a lower clad layer 5 of p type AlGaAs, grown in the reverse order from the lower clad layer 5 in manufacturing. Then, an n side electrode 1 is formed on the upper surface of the epitaxial wafer while a p side electrode 8 is formed on the lower surface thereof. A mesa groove 14 for cleavage is formed on the lower surface of the substrate 7.
Referring to FIG. 1B, the epitaxial wafer is cleft along the mesa groove 14 by applying force to the epitaxial wafer in the direction of an arrow 15 in the figure. The cleavage plane obtained from this cleavage forms a laser resonator plane 16 for outputting laser light.
Several methods are known for foring such cleavage plane. For example, applying force by pinching the epitaxial wafer with a pair of tweesers or applying force to the wafer surface opposite to the mesa groove 14 with a sharp edged tool such as a surgical knife has been known as a typical method.
The operation of the semiconductor laser device shown in FIG. 1B will be hereinafter described. In FIG. 1B, when a forward voltage is applied between the n side electrode 1 and the p side electrode 8, a current flows between both electrodes 1 and 8 implanting minority carriers into the active layer 4. Consequently, laser oscillation is performed and laser light is outputted from the laser resonator plane 16.
However, in a conventional semiconductor laser device manufactured according to the above described method, the semiconductor laser device is in the shape of a bar after the formation of the laser resonator plane, as shown in FIG. 1B, presenting a problem that the handling thereof is troublesome.
Since the process for forming the laser resonator plane as shown in FIG. 1B depends on skilled workers, there is a problem that the efficiency in working is low.
In addition, in incorporating the semiconductor laser device into various machines, a photodiode for monitoring laser light output must be provided at the back of the semiconductor laser device generally; however, in a conventional semiconductor laser device as described above, the photodiode is not intergrated on the same substrate with the result, so that there is a problem that the semiconductor laser device and the photodiode must be separately incorporated.